Spinal muscular atrophy (SMA) is an autosomal recessive disorder characterized by progressive muscle weakness due to deterioration of motor neurons. SMA results from homozygous mutation of the SMN (survival motor neuron) 1 gene. A nearly identical copy, SMN2, fails to protect from development of SMA as its major mRNA undergoes alternative splicing that encodes for an unstable SMN protein. This alternative spliced product excludes exon 7. A small fraction of the SMN2 transcripts include exon 7 and encode the same SMN protein as does SMN1. This application describes a two-year hit-to-lead discovery program to identify drug-like compounds that increase intracellular SMN protein levels. Using a redesigned, improved, and validated cell-based reporter assay, the investigators identified activators of SMN protein expression from a library of 115,000 diverse chemical entities. Specific Aim 1 of this project is to evaluate the biological activity of these hits in SMA cell culture models and determine the mechanism of action for each compound. Specific Aim 2 will then strives to define structure activity relationships (SAR) for lead optimization, and test available structural analogues or synthesize a small focused library of related compounds to increase activity and drug-like characteristics of the lead compounds. Importantly, the application merges the experience and capabilities of the laboratories investigating the molecular biology of SMA with the expertise of a Center devoted to the development of novel therapies for neurodegenerative diseases that reproduces a drug company approach to identify pharmacologically active compounds. The predicted outcome of this application is the identification and characterization of chemically suitable compounds with nanomolar activities in cell-based assays that can be entered into a preclinical program in SMA mouse models. The ultimate goal is to develop an effective drug for treatment of spinal muscular atrophy, the leading genetic cause of infant mortality.